Imaging apparatus, method for controlling the same, and storage medium

ABSTRACT

A method is provided for controlling an apparatus, the method comprising, detecting, as focus detection, a defocus amount based on a signal for a focus detection processing, controlling a focusing lens movement based on the defocus amount, and determining, as saturation determination, whether a subject to be subjected to the focus detection processing is a saturated subject. In a case where a state where a variation in the detected defocus amount of an image of the subject to be subjected to the focus detection processing or a variation in a moving amount of an imaging plane is smaller than a predetermined value continuously occurs the predetermined number of times or continues for a predetermined time duration, the subject to be subjected to the focus detection processing is determined to be a saturated subject in the saturation determination.

BACKGROUND OF THE INVENTION Field of the Invention

The aspect of the embodiments relates to an apparatus having a focusingadjustment function, a method for controlling the apparatus, and astorage medium.

Description of the Related Art

In a case where a subject includes, for example, a high-luminance lightsource, an imaging signal corresponding to the light source issaturated. The saturated imaging signal is observed as a saturationlevel at a constant value.

Japanese Patent Application Laid-Open No. 2008-185823 discusses a focusdetection apparatus that detects the presence or absence of saturationdue to a point light source subject at low cost. To achieve this, thefocus detection apparatus uses an imaging signal from an image sensorafter removing signal components having a predetermined frequency orlower to determine the presence or absence of signal saturation in theimaging signal before removing signal components.

However, the prior art discussed in Japanese Patent ApplicationLaid-Open No. 2008-185823 observes only the presence or absence of asaturating signal and therefore may be unable to accurately determinewhether a saturated subject is present.

SUMMARY OF THE INVENTION

As a technical feature of the aspect of the embodiments, there isprovided a method including, detecting, as focus detection, a defocusamount based on a signal for focus detection processing, controlling afocusing lens movement based on the defocus amount, and determining, assaturation determination, whether a subject to be subjected to the focusdetection processing is a saturated subject. In a case where a statewhere a variation in the detected defocus amount of an image of thesubject to be subjected to the focus detection processing or a variationin a moving amount of an imaging plane is smaller than a predeterminedvalue continuously occurs the predetermined number of times or continuesfor a predetermined time duration, the subject to be subjected to thefocus detection processing is determined to be a saturated subject inthe saturation determination.

Further features of the disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a lens-interchangeable camerasystem.

FIG. 2A illustrates an example of a pixel configuration with anon-imaging plane phase difference method, and FIG. 2B illustrates anexample of a pixel configuration with an imaging plane phase differencemethod.

FIG. 3 is a flowchart illustrating processing of an imaging apparatus.

FIG. 4 is a flowchart illustrating automatic focusing (AF) processing.

FIG. 5 is a flowchart illustrating focus detection processing.

FIG. 6 illustrates a focus detection region.

FIGS. 7A, 7B, 7C, and 7D are conceptual views illustrating a differencein AF signals (a pair of image signals) between a case where the focusdetection region includes a saturated subject and a case where the focusdetection region does not include a saturated subject.

FIG. 8 is conceptual view illustrating a relation between a lensposition and a defocus amount in a case where the focus detection regionincludes a saturated subject.

FIGS. 9A, 9B, 9C, and 9D are conceptual views illustrating AF signals (apair of image signals) for each lens position in a case where the focusdetection region includes a saturated subject.

FIG. 10 is a flowchart illustrating lens drive according to a firstexemplary embodiment.

FIG. 11 is a flowchart illustrating saturated subject determination.

FIG. 12 is a flowchart illustrating first deemed in-focus drive.

FIG. 13 is a flowchart illustrating lens drive.

FIG. 14 is a flowchart illustrating second deemed in-focus drive.

FIG. 15 is a flowchart illustrating lens drive according to a secondexemplary embodiment.

FIG. 16 is a flowchart illustrating lens drive according to a thirdexemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiment of the disclosure will be described in detail belowwith reference to the accompanying drawings.

Elements of one embodiment may be implemented by hardware, firmware,software or any combination thereof. The term hardware generally refersto an element having a physical structure such as electronic,electromagnetic, optical, electro-optical, mechanical,electro-mechanical parts, etc. A hardware implementation may includeanalog or digital circuits, devices, processors, applications specificintegrated circuits (ASICs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), or any electronic devices. The termsoftware generally refers to a logical structure, a method, a procedure,a program, a routine, a process, an algorithm, a formula, a function, anexpression, etc. The term firmware generally refers to a logicalstructure, a method, a procedure, a program, a routine, a process, analgorithm, a formula, a function, an expression, etc., that isimplemented or embodied in a hardware structure (e.g., flash memory,ROM, EPROM). Examples of firmware may include microcode, writablecontrol store, micro-programmed structure. When implemented in softwareor firmware, the elements of an embodiment may be the code segments toperform the necessary tasks. The software/firmware may include theactual code to carry out the operations described in one embodiment, orcode that emulates or simulates the operations. The program or codesegments may be stored in a processor or machine accessible medium. The“processor readable or accessible medium” or “machine readable oraccessible medium” may include any medium that may store information.Examples of the processor readable or machine accessible medium that maystore include a storage medium, an electronic circuit, a semiconductormemory device, a read only memory (ROM), a flash memory, a UniversalSerial Bus (USB) memory stick, an erasable programmable ROM (EPROM), afloppy diskette, a compact disk (CD) ROM, an optical disk, a hard disk,etc. The machine accessible medium may be embodied in an article ofmanufacture. The machine accessible medium may include information ordata that, when accessed by a machine, cause the machine to perform theoperations or actions described above. The machine accessible medium mayalso include program code, instruction or instructions embedded therein.The program code may include machine readable code, instruction orinstructions to perform the operations or actions described above. Theterm “information” or “data” here refers to any type of information thatis encoded for machine-readable purposes. Therefore, it may includeprogram, code, data, file, etc.

All or part of an embodiment may be implemented by various meansdepending on applications according to particular features, functions.These means may include hardware, software, or firmware, or anycombination thereof. A hardware, software, or firmware element may haveseveral modules coupled to one another. A hardware module is coupled toanother module by mechanical, electrical, optical, electromagnetic orany physical connections. A software module is coupled to another moduleby a function, procedure, method, subprogram, or subroutine call, ajump, a link, a parameter, variable, and argument passing, a functionreturn, etc. A software module is coupled to another module to receivevariables, parameters, arguments, pointers, etc. and/or to generate orpass results, updated variables, pointers, etc. A firmware module iscoupled to another module by any combination of hardware and softwarecoupling methods above. A hardware, software, or firmware module may becoupled to any one of another hardware, software, or firmware module. Amodule may also be a software driver or interface to interact with theoperating system running on the platform. A module may also be ahardware driver to configure, set up, initialize, send and receive datato and from a hardware device. An apparatus may include any combinationof hardware, software, and firmware modules.

<Configuration of Imaging Apparatus>

A first exemplary embodiment will be described below centering on a casewhere the disclosure is applied to a lens-interchangeable imagingapparatus.

The configuration of the imaging apparatus according to the presentexemplary embodiment will be described below with reference to FIG. 1.FIG. 1 is a block diagram of a lens-interchangeable camera system 10.The lens-interchangeable camera system 10 includes a camera body 200(imaging apparatus main body) and a lens apparatus 100 (imaging opticalsystem) which is attachable to and detachable from the camera body 200.The lens apparatus 100 is detachably (interchangeably) attached to thecamera body 200 via a mount portion (not illustrated) having anelectrical contact unit. The present exemplary embodiment is alsoapplicable to an imaging apparatus integrally formed of a lens apparatusand a camera body.

The lens apparatus 100 includes an imaging lens 101, a diaphragm andshutter 102, a focusing lens 103, a zoom actuator 107, a diaphragmshutter actuator 108, a focus actuator 104, and a lens controller 105.The imaging lens 101 includes a zoom mechanism. The diaphragm andshutter 102 controls the light amount. The focusing lens 103 is used forfocusing on the image sensor 201 (described below). The zoom actuator107 rotates a cam barrel (not illustrated) to move the zoom mechanismincluded in the imaging lens 101 in the optical axis direction, thusperforming a zooming operation. The diaphragm shutter actuator 108controls the opening diameter of the diaphragm and shutter 102 to adjustthe imaging light amount, and performs exposure time control at the timeof still image capturing. The focus actuator 104 moves the focusing lens103 in the optical axis direction to perform a focusing adjustmentoperation. The lens controller 105 controls the entire lens apparatus100 to connect with the camera body 200 via a communication bus 106.

The camera body 200 includes the image sensor 201, an analog-to-digital(A/D) converter 202, an image processing unit 203, an automatic focusing(AF) signal processing unit 204, and a format converter 205. The imagesensor 201 functions as a light receiving unit (photoelectric conversionelements) for converting reflected light from the subject into anelectrical signal. The A/D converter 202 includes a cadmium sulfide(CDS) circuit for removing output noise of the image sensor 201, and anonlinear amplification circuit for performing nonlinear amplificationbefore analog-to-digital (AD) conversion. According to the presentexemplary embodiment, the AF signal processing unit 204 includes anacquisition unit 204 a and a calculation unit 204 b. The camera body 200includes a high-speed built-in memory (dynamic random access memory(DRAM)) 206, such as a random access memory (RAM), and uses the memoryas a high-speed buffer (temporary image storage unit) or a work memoryin image compression and decompression.

The camera body 200 further includes an image recording unit 207, asystem control unit 209, a lens communication unit 210, an automaticexposure (AE) processing unit 211, an image display memory (video RAM(VRAM)) 212, and an image display unit 213. The image recording unit 207includes a recording medium, such as a memory card and the interface.The system control unit 209 controls the system including imagingsequences. The lens communication unit 210 is connected to the lenscontroller 105 via the communication bus 106 and performs communicationbetween the camera body 200 and the lens apparatus 100. The imagedisplay unit 213 displays images, operation assistance information, andcamera statuses. At the time of image capturing, the image display unit213 displays an imaging screen and a focus detection region.

The camera body 200 includes an operation unit 214 for the user tooperate the camera body 200. The camera body 200 includes menu switchesfor performing various settings for imaging functions and imagereproduction settings of the lens-interchangeable camera system 10, andan operation mode changeover switch for switching between the imagingmode and the reproduction mode. An imaging mode switch 215 is used forselecting the imaging mode, such as a macro mode and a sports mode. Amain switch 216 is used for turning ON power of the camera body 200. Aswitch (SW1) 217 is used for performing imaging standby operations, suchas automatic focusing adjustment (AF) and automatic exposure (AE). Aswitch (SW2) 218 is used for capturing an image after operating theswitch SW1.

An image sensor 201 including a charge coupled device (CCD) sensor orcomplementary metal oxide semiconductor (CMOS) sensor photoelectricallyconverts a subject image (optical image) formed through the imagingoptical system of the lens apparatus 100 and then outputs a pixel signal(image data). More specifically, a light flux incident from the imagingoptical system forms an image on the light receiving surface of theimage sensor 201, and is converted into signal charges according to theincident light amount by the pixels (photodiodes) arranged on the imagesensor 201. Signal charges accumulated in each photodiode aresequentially read from the image sensor 201 as a voltage signalcorresponding to the signal charges based on a drive pulse output from atiming generator 208 according to an instruction of the system controlunit 209.

Each pixel of the image sensor 201 according to the present exemplaryembodiment includes a pair of two photodiodes A and B, and one microlens provided for the pair of the photodiodes A and B (each micro lensshares the photodiodes A and B). More specifically, the image sensor 201includes a plurality of two-dimensionally arranged micro lenses each ofwhich having a pair of photodiodes (a first photoelectric converter anda second photoelectric converter). Each pixel divides incident light byusing a micro lens to form a pair of optical images on the pair of thephotodiodes A and B and outputs a pair of pixel signals (A image signaland B image signal) used for AF signals (described below) from the pairof the photodiodes A and B. An imaging signal (A+B image signal) can beobtained by adding the outputs of the pair of the photodiodes A and B.

A pair of image signals as the AF signals (signals for focus detection)used for AF based on the imaging plane phase difference detection method(imaging plane phase difference AF) can be obtained by combining theplurality of the A image signals and the plurality of the B imagesignals output from the plurality of pixels. An AF signal processingunit 204 (described below) performs the correlation calculation for thepair of image signals to calculate a phase difference as a shift amountbetween the pair of image signals (image shift amount), and furthercalculates the defocus amount (including the defocusing direction) ofthe imaging optical system based on the image shift amount.

Thus, the image sensor 201 photoelectrically converts an optical imageformed by receiving a light flux that passed the imaging optical systemof the lens apparatus 100 into an electrical signal and outputs imagedata (image signal). The image sensor 201 according to the presentexemplary embodiment is provided with two photodiodes for each microlens, and is able to generate an image signal to be used for focusdetection based on the imaging plane phase difference AF method. Thenumber of photodiodes sharing one micro lens can be changed, e.g., fourphotodiodes may be provided for each micro lens.

FIG. 2A schematically illustrates an example of a pixel configurationnot conforming to the imaging plane phase difference AF method. FIG. 2Bschematically illustrates an example of a pixel configuration conformingto the imaging plane phase difference AF method. Both the pixelconfigurations illustrated in FIGS. 2A and 2B use the Bayer array. Rdenotes a red color filter, B denotes a blue color filter, and Gr and Gbdenote green color filters. In the pixel configuration illustrated inFIG. 2B conforming to the imaging plane phase difference AF method, onepixel (drawn with solid lines) in a pixel configuration not conformingto the imaging plane phase difference AF method illustrated in FIG. 2Aincludes the horizontally divided photodiodes A and B illustrated inFIG. 2B. The photodiodes A and B (the first and the second photoelectricconverters) receive light fluxes that have passed different pupilregions in the imaging optical system.

Since the photodiodes A and B receive light fluxes that have passeddifferent exit pupil regions of the imaging optical system in this way,the B image signal has a parallax with respect to the A image signal.One image signal (A or B image signal) out of the above-describedimaging signal (A+B image signal) and a pair of parallax image signalshas a parallax. The pixel division method illustrated in FIG. 2B is tobe considered as an example, and other pixel configurations are alsoapplicable. For example, each pixel may be divided in the verticaldirection or divided in each of the horizontal and the verticaldirections (i.e., divided into four pieces). The same single imagesensor may include a plurality of types of pixels divided by differentdivision methods.

The present exemplary embodiment has been described above centering on aconfiguration where a plurality of photoelectric converters is disposedfor each micro lens, and a pupil-divided light flux is incident to eachphotoelectric converter. However, the aspect of the embodiments is notlimited thereto. For example, in the configuration of a focus detectionpixel, one photodiode may be provided under the micro lens, and pupildivision may be performed by horizontally or vertically blocking lightby using a light shielding layer. A pair of focus detection pixels maybe discretely disposed in the array of a plurality of imaging pixels,and a pair of image signals may be acquired from the pair of focusdetection pixels.

The imaging signal read from the image sensor 201 and the AF signals areinput to the A/D converter 202. The A/D converter 202 subjects theimaging signal and the AF signals to correlated double sampling forremoving reset noise, gain adjustment, and digitization. The A/Dconverter 202 outputs the imaging signal to the image processing unit203 and outputs the AF signals to the AF signal processing unit 204.

The AF signal processing unit 204 (the acquisition unit 204 a) acquiresthe AF signals (a pair of image signals including a first signal (Aimage signal) and a second signal (B image signal)) output from the A/Dconverter 202. The AF signal processing unit 204 (the calculation unit204 b) performs the correlation calculation based on the AF signals tocalculate the image shift amount, and calculates the defocus amountbased on the image shift amount. The AF signal processing unit 204 (thecalculation unit 204 b) ranks the reliability based on the reliabilityinformation of the AF signals (coincidence of the two images, steepnessof the two images, contrast information, saturation information, anddefect information). The defocus amount and the reliability information(reliability) calculated by the AF signal processing unit 204 are outputto the system control unit 209.

<Imaging Processing>

Operations of the camera body 200 according to the present exemplaryembodiment will be described below with reference to FIG. 3. FIG. 3 is aflowchart illustrating operations of the camera body 200. Each step ofthe flowchart illustrated in FIG. 3 is executed by each unit basedmainly on instructions of the system control unit 209.

In step S301, the system control unit 209 controls the AE processingunit 211 to perform AE processing on the output signal from the imageprocessing unit 203. In step S302, the system control unit 209determines whether the switch 217 (SW1) is ON. If the switch 217 (SW1)is ON (YES in step S302), the processing proceeds to step S303. If theswitch 217 (SW1) is OFF (NO in step S302), the processing returns tostep S301.

In step S303, the system control unit 209 performs an AF operation. TheAF operation will be described in detail below. In step S304, the systemcontrol unit 209 determines whether the switch 217 (SW1) is ON. If theswitch 217 (SW1) is ON (YES in step S304), the processing proceeds tostep S305. If the switch 217 (SW1) is OFF (NO in step S304), theprocessing returns to step S301.

In step S305, the system control unit 209 determines whether the switch218 (SW2) is ON. If the switch 218 (SW2) is OFF (NO in step S305), theprocessing returns to step S304. If the switch 218 (SW2) is ON (YES instep S305), the processing proceeds to step S306. In step S306, thesystem control unit 209 performs an imaging operation. Then, theprocessing returns to step S301.

<Details of AF Processing (Step S303)>

The AF processing (step S303) according to the present exemplaryembodiment will be described below with reference to FIG. 4.

Each step in the flowchart illustrated in FIG. 4 is executed mainly bythe AF signal processing unit 204 and the system control unit 209.

In step S401, the system control unit 209 controls the AE processingunit 211 to perform the AE processing on the output signal of the imageprocessing unit 203. In step S402, the AF signal processing unit 204performs focus detection processing by using the pair of image signalsto calculate the defocus amount and reliability. The focus detectionprocessing will be described in detail below.

In step S403, the system control unit 209 drives (moves) the focusinglens 103 based on the defocus amount and reliability calculated in stepS402. Lens drive will be described in detail below.

In step S404, the system control unit 209 determines whether the focusstate (in-focus/defocus) is determined. If the focus state is notdetermined (NO in step S404), the processing returns to step S402. Ifthe focus state is determined (YES in step S404), the processingproceeds to step S405. In step S405, the system control unit 209displays the in-focus or defocus state. The processing then exits thisflowchart.

<Details of Focus Detection Processing (Step S402)>

The focus detection processing (step S402) will be described in detailbelow with reference to FIG. 5. Each step illustrated in FIG. 5 isexecuted mainly by the system control unit 209 or by the AF signalprocessing unit 204 based on an instruction of the system control unit209.

In step S501, the AF signal processing unit 204 (the system control unit209) sets a focus detection region over an optional range in the imagesensor 201. In step S502, the AF signal processing unit 204 acquires thepair of image signals (A and B image signals) for focus detection fromthe image sensor 201 for the focus detection region set in step S501. Instep S503, the AF signal processing unit 204 performs the line averagingin the vertical direction on the pair of image signals acquired in stepS502. The line averaging reduces the effect of noise in the imagesignals. In step S504, the AF signal processing unit 204 performs thefilter processing of extracting signal components in a predeterminedfrequency band out of the pair of image signals having been subjected tothe line averaging in step S503.

In step S505, the AF signal processing unit 204 calculates a correlationamount based on the pair of image signals after the filter processing instep S504. In step S506, the AF signal processing unit 204 calculatescorrelation variation based on the correlation amount calculated in stepS505. In step S507, the AF signal processing unit 204 calculates animage shift amount based on the correlation variation calculated in stepS506. In step S508, the AF signal processing unit 204 calculates thereliability of the image shift amount calculated in step S507. In stepS509, the AF signal processing unit 204 converts the image shift amountinto the defocus amount.

In step S510, the system control unit 209 determines whether thecalculation for the filter processing in step S504 is completed for allof filter types. If the filter processing is completed for all of filtertypes (YES in step S510), the processing proceeds to step S511. If thefilter processing is completed not for all of filter types (NO in stepS510), the processing returns to step S504. According to the presentexemplary embodiment, in the filter processing in step S504, the AFsignal processing unit 204 performs, for example, the filter processingby using three different types of frequency band-pass filters (low-passfilter, middle-band-pass filter, and high-pass filter) in the horizontaldirection, on the pair of image signals having been subjected to theline averaging. The low-pass, middle-band-pass, and high-pass filtersrefer to relative frequency values of frequency components extracted byeach filter, not absolute frequency values. In step S510, the systemcontrol unit 209 determines whether the processing in steps S504 to S509is completed for all of the three different frequency bands.

In step S511, the system control unit 209 performs the in-focusdetermination. The in-focus determination refers to processing forselecting the defocus amount calculated by using the filters. Morespecifically, the system control unit 209 (determination unit) selects(determines) a combination of the defocus amount and reliability out ofthe three combinations of the defocus amount and reliability calculatedin a series of the operations in steps S504 to S509.

<Issues of Saturated Subject>

The focus detection region (AF region) set in step S501 illustrated inFIG. 5 will be described in detail below with reference to FIG. 6. FIG.6 illustrates a focus detection region 602 on a pixel array 601 of theimage sensor 201. Shift regions 603 on both sides of the focus detectionregion 602 are regions required for the correlation calculation. Thus, aregion 604 including the focus detection region 602 and the shiftregions 603 is a pixel region required for the correlation calculation.Referring to FIG. 6, p, q, s, and t denote coordinates in the horizontaldirection (x-axis direction). p and q denote the x coordinates of thestart and the end points of the region 604 (pixel region), respectively.s and t denote the x coordinates of the start and the end points thefocus detection region 602, respectively.

FIGS. 7A, 7B, 7C, and 7D conceptually illustrate differences in AFsignals (a pair of image signals) between a case where the focusdetection region 602 illustrated in FIG. 6 includes no saturated subject(FIGS. 7A and 7B) and a case where the focus detection region 602includes a saturated subject (FIGS. 7C and 7D). Referring to each ofFIGS. 7A, 7B, 7C, and 7D, the solid lines 701 and 711 denote one of thepair of the image signals, i.e., the A image signal, and the brokenlines 702 and 712 denote the other of the pair the image signals, i.e.,the B image signal. The chain double-dashed lines denote the centers ofgravity of the image signals, and the dot-dash lines denote thesaturation level of the image sensor 201 (the limit of the chargeaccumulation capacity of the photodiodes).

FIG. 7A illustrates the A image signal 701 and the B image signal 702 ina case where a point light source that is out of focus by a defocusamount D, in the focus detection region 602 is in the non-saturatedstate (the image signals have not reached the saturation level) withproper exposure. To simplify the description, FIG. 7B illustrates astate where the B image signal 702 is shifted by D from the stateillustrated in FIG. 7A, i.e., the state of the best correlation.

FIG. 7C illustrates a case where the output of the point light sourceillustrated in FIG. 7A is a high luminance, and the amount of incidentlight to the photodiodes exceeds the saturation level. Morespecifically, the image signals illustrated in FIG. 7C provide, as awhole, higher signal levels than the image signals illustrated in FIG.7A. For example, referring to FIG. 7A, the signal level of the B imagesignal 702 at an edge of the point light source (the vertical dottedline) is drawn by the horizontal dotted line. Referring to FIG. 7C, thecorresponding signal level of the B image signal 712 provides a highsignal level which coincides with the saturation level.

More specifically, FIG. 7C illustrates the A image signal 711 and the Bimage signal 712 in a case where a point light source that is out offocus by a defocus amount D, in the focus detection region 602 is in asaturated state and is a high luminance. Referring to FIG. 7C, in theoutput region exceeding the saturation level drawn by the dot-dash line,the outputs of the A image signal 711 and the B image signal 712 areclipped to the constant value at the saturation level. In this case,FIG. 7D illustrates a state where the B image signal 712 is shifted by d(D>d) from the state illustrated in FIG. 7C, i.e., the state of the bestcorrelation.

In FIG. 7A, by signals at peaks at which a parallax-based image shiftbetween the A and the B image signals remarkably occurs, as a result ofthe correlation calculation, a correct defocus amount D is calculated.By contrast, the peak cannot be detected in FIG. C (the image signalsare clipped to the constant value at the saturation level) because ofsaturation. In this case, as a result of the correlation calculation, adefocus amount d smaller than the actual defocus amount D ismisdetected.

<Relation Between Lens Position and Defocus Amount when Focus DetectionRegion Includes Saturated Subject>

FIG. 8 conceptually illustrates the relation between the lens positionand the defocus amount in a case where the focus detection region 602illustrated in FIG. 6 includes a saturated subject. In FIG. 8, in aregion S in which the focus state is close to be in-focus state, therelation between the lens position and the defocus amount almostcoincides with a linear state (drawn by the dotted line). Morespecifically, the reliability of the calculated defocus amount is highin the region S, and directly driving the lens causes no problem. Bycontrast, the image is out of focus in the regions L, the relationbetween the lens position and the defocus amount largely deviates fromthe linear state (drawn by the dotted line), i.e., the defocus amount isapproximately constant regardless of the lens position.

FIGS. 9A and 9B illustrate AF signals (a pair of image signals) atpoints (a) and (b) in a region L, respectively. FIGS. 9C and 9Dillustrate the AF signals at points (c) and (d) in the region S,respectively. Referring to each of FIGS. 9A, 9B, 9C, and 9D, the solidline 911 denotes one of the pair of the image signals, i.e., the A imagesignal, and the broken line 912 denotes the other of the pair the imagesignals, i.e., the B image signal.

In defocus states illustrated in FIGS. 9A and 9B (the region Lillustrated in FIG. 8), the half value widths of the A image signal 911and the B image signal 912 increase, and the range where the outputbecomes constant at the saturation level increases. Thus, the influenceof the portion having a constant output, on the correlation calculationbecomes dominant, resulting in decreased variation in the defocusamount, as in the region L illustrated in FIG. 8.

In the area in which the focus state is close to be in-focus stateillustrated in FIGS. 9C and 9D (the region S illustrated in FIG. 8), thehalf value widths of the A image signal 911 and the B image signal 912decrease, and the range where the output becomes constant at thesaturation level also decreases. Thus, the influence of the shiftamounts of the skirts of the A image signal 911 and the B image signal912, on the correlation calculation becomes dominant, resulting in avarying defocus amount according to the lens position, as in the regionS illustrated in FIG. 8.

More specifically, in the case of a saturated subject, the influence ofthe portion having a constant output of the original peak portion, onthe correlation calculation becomes dominant in the defocus state,resulting in decreased variation in the defocus amount.

In performing automatic focusing in the frame including a saturatedsubject, a defocus amount smaller than an actual out-of-focus amount iscalculated. In this case, the in-focus determination criterion is to bechanged or devise the driving method in consideration of small variationin the defocus amount in the defocus state.

FIGS. 7A, 7B, 7C, and 7D, 8, 9A, 9B, 9C, and 9D are schematic views. Thedegree of the above-described influences of the saturation on thecorrelation calculation varies according to the luminance, size, andshape of the saturated subject and the sensor characteristics. Further,in a general scene, the focus detection region 602 may include ahigh-contrast subject other than a saturated subject. In this case, thecorrelation of the image of the high-contrast subject may change thecharacteristics.

<Details of Lens Drive (Step S403) According to First ExemplaryEmbodiment>

Lens drive (step S403) according to a first exemplary embodiment of thedisclosure will be described below with reference to FIG. 10. Each stepillustrated in FIG. 10 is executed mainly by the system control unit209.

In step S1001, the system control unit 209 sets the defocus amountselected in step S511 to the lens drive amount (drive amount). In stepS1002, the system control unit 209 drives the lens by the drive amountset in step S1001. In step S1003, the system control unit 209 performsthe focus detection processing in step S402.

In step S1004, as described above with reference to FIGS. 7A to 9D, thesystem control unit 209 determines whether the image to be subjected tothe focus detection is a saturated subject which can be misdetected. Thesaturation determination will be described in detail below. In stepS1005, the system control unit 209 determines whether the reliability ishigh with reference to the reliability calculated in step S1003 (stepS508). If the reliability is low (NO in step S1005), the processingreturns to step S1001. If the reliability is high (YES in step S1005),the processing proceeds to step S1006.

In step S1006, the system control unit 209 determines whether the targetposition determined based on the defocus amount calculated in step S1003(step S507) is within the range of an in-focus management width. If thetarget position is within the range of the in-focus management width(YES in step S1006), the processing proceeds to step S1007. In stepS1007, the system control unit 209 determines the focus state as thein-focus state. The processing exits this flowchart. This is because thephase difference of the image to be subjected to the focus detectionbecomes zero or nearly zero. For the in-focus management width, a valueof ±1 Fδ or less is set because the value serves as a threshold valuefor determining the focus state as the in-focus state. The in-focusmanagement width is set in the region S (close to be in-focus)illustrated in FIG. 8. In the region S, the relation between the lensposition and the defocus amount is linear and has high reliability, asdescribed above with reference to FIG. 8. Thus, the system control unit209 determines the focus state as the in-focus state and then terminateslens drive (terminates a focusing operation).

If the target position is out of the range of the in-focus managementwidth (NO in step S1006), the processing proceeds to step S1008. In thiscase, the system control unit 209 performs the focus detection againafter completion of focusing lens drive.

As in the region L illustrated in FIG. 8, the defocus amount may bepossibly misdetected under the influence of a saturated subject. Thus,in step S1008, the system control unit 209 determines the state of thesaturated subject flag determined in step S1004. If the saturatedsubject flag is OFF (if the focusing detection target is not a saturatedsubject) (NO in step S1008), i.e., the system control unit 209determines that the defocus amount is not misdetected, and theprocessing proceeds to step S1009. In step S1009, the system controlunit 209 determines whether the defocus amount calculated in step S1003(step S507) is equal to or less than a first deemed in-focus width. Ifthe calculated defocus amount is larger than the first deemed in-focuswidth (NO in step S1009), the processing returns to step S1001. If thecalculated defocus amount is equal to or less than the first deemedin-focus width (YES in step S1009), the processing proceeds to stepS1011. In step S1011, the system control unit 209 performs the firstdeemed in-focus drive. The processing then exits this flowchart.

The deemed in-focus drive which is performed in step S1011 refers todrive control processing in which the lens is driven a predeterminednumber of times, the focus state is determined as the in-focus state,and forcibly terminating lens drive is forcibly terminated (describedbelow with reference to FIG. 12). The deemed in-focus drive is a generaltechnique for addressing such a trouble that the in-focus state cannotbe obtained while the subject is moving during one-shot AF and a troublethat the in-focus state can be hardly obtained because of the degradedlens drive accuracy due to degradation over time. The deemed in-focusdrive will be described in detail below.

As described above, the deemed in-focus drive in step S1011 forciblyterminates lens drive. Thus, to start the deemed in-focus drive, thereliability of the focus detection is high (step S1005) and that thelens exists in a region in which in-focus state is obtained to a certainextent. Thus, in one embodiment, the first deemed in-focus width fordetermining whether to start the deemed in-focus drive is set to a valueof about ±5 Fδ.

If the saturated subject flag is ON (if the focusing detection target isa saturated subject) (YES in step S1008), the possibility that thedefocus amount is misdetected is high, and the processing proceeds toS1010. In step S1010, the system control unit 209 determines whether thedefocus amount calculated in step S1003 (S507) is equal to or less thana second deemed in-focus width. if the focusing detection target is asaturated subject, a defocus amount smaller than the actual out-of-focusamount is detected in error and tends not to vary, as described abovewith reference to FIGS. 7A, 7B, 7C, 7D, 8, 9A, 9B, 9C, and 9D. Thus, thesecond deemed in-focus width is set to a value smaller than the firstdeemed in-focus width.

More specifically, in a case where the focusing detection target is asaturated subject, to avoid defocusing, starting the deemed in-focusdrive in the region L illustrated in FIG. 8 is to be avoided. Thus, thesecond deemed in-focus width is to be set to a value smaller than thedefocus amount which is misdetected in the region L. Accordingly, thesecond deemed in-focus width to a value of about ±2 Fδ is set. If thecalculated defocus amount is larger than the second deemed in-focuswidth (NO in step S1010), the processing returns to step S1001. If thecalculated defocus amount is equal to or less than the second deemedin-focus width (YES in step S1010), the processing proceeds to stepS1011. In step S1011, the system control unit 209 performs the firstdeemed in-focus drive. Then, the processing exits this flowchart.

According to the present exemplary embodiment, the relation between thedeemed in-focus width |A|, the first deemed in-focus width |B|, and thesecond deemed in-focus width |C| is as follows:|A|<|C|<|B|  (1)

In a case where a saturated subject is detected, the threshold value forstarting the deemed in-focus drive is set to a value smaller than thatin a usual case (when no saturated subject is detected) in considerationof the misdetection of a defocus amount smaller than the actualout-of-focus amount. This prevents the in-focus determination in thedefocus state.

The saturated subject determination (step S1004) will be described belowwith reference to FIG. 11.

In step S1101, the system control unit 209 determines whether avariation in the defocus amount (defocus variation) is equal to or lessthan a predetermined threshold value (saturated subject ΔdefocusTh). Thedefocus variation is a difference between the defocus amount selected instep S511 and the last defocus amount. The saturated subject ΔdefocusThis a threshold value determined by the amount of the back-and-forthmovement of lens driven in step S1002 or the moving amount of the imageplane, based on the defocus amount selected in step S511. Morespecifically, the system control unit 209 determines whether the defocusamount varies based on the variation in the defocus amount calculated instep S511 with respect to the variation in the defocus amount expectedfrom the lens drive amount or the moving amount of the image plane.

If the system control unit 209 determines that the defocus variation islarger than the predetermined threshold value, ΔdefocusTh, (there is avariation in defocus amount) (NO in step S1101), the processing proceedsto step S1105. In step S1105, the system control unit 209 sets thesaturated subject flag to OFF. Then, the processing exits thisflowchart. If the system control unit 209 determines that the defocusvariation is equal to or less than the predetermined threshold value,ΔdefocusTh, (there is no variation in defocus amount) (YES in stepS1101), the processing proceeds to step S1102. In step S1102, the systemcontrol unit 209 increments saturated subject Count.

In step S1103, the system control unit 209 determines whether saturatedsubject Count is equal to or larger than a predetermined threshold value(saturated subject CountTh), and detects the saturated subject. Morespecifically, the system control unit 209 determines whether a state inwhich the defocus variation is equal to or less than the predeterminedthreshold value ΔdefocusTh (there is no defocus variation) hascontinuously occurred the predetermined number of times. Thisdetermination is made to prevent misdetection that there is no defocusvariation due to a variation in the correlation calculation, andmisdetection that occurs when the lens drive response is poor. Thus, inone embodiment, saturated subject Count is set to a value of 2 or more.While the number of times is used for the threshold value, a timeduration (time period) may be used for the threshold value(predetermined time duration) to prevent misdetection. If subject Countis equal to or larger than the threshold value (saturated subjectCountTh), i.e., when a saturated subject is detected (YES in stepS1103), the processing proceeds to step S1104. In step S1104, the systemcontrol unit 209 sets the saturated subject flag to ON. The processingthen exits this flowchart. If saturated subject Count is smaller thanthe threshold value (saturated subject CountTh) (NO in step S1103), theprocessing proceeds to step S1105. In step S1105, the system controlunit 209 sets the saturated subject flag to OFF. The processing thenexits this flowchart.

In this flowchart, the system control unit 209 detects a saturatedsubject depending only on whether the defocus amount has changed.However, additional steps may be included in this flowchart. Examples ofadditional steps include a step for determining a saturated subject onlyin a case where the number of pixels saturated in pixel units isdetermined to be equal to or larger than a threshold value, and a stepfor determining whether the defocus amount is within a predeterminedrange in consideration of the misdetection of the defocus amount as avalue smaller than the actual out-of-focus amount. This enables asaturated subject to be detected with favorable accuracy.

The deemed in-focus drive (step S1011) will be described below withreference to FIG. 12.

In step S1201, the system control unit 209 initializes the number ofdeemed in-focus drives (hereinafter referred to as deemed Count). Instep S1202, the system control unit 209 sets the defocus amountcalculated in the focus detection processing in step S1003 to the lensdrive amount (drive amount). In step S1203, the system control unit 209drives the lens by the drive amount set in step S1001 and thenincrements deemed count.

In step S1204, the system control unit 209 starts the flowchart of thefocus detection processing (step S402) and calculates the defocusamount. In step S1205, the system control unit 209 determines whetherthe defocus amount calculated in step S1204 is equal to or less than thein-focus management width. If the calculated defocus amount is equal toor less than the in-focus management width (YES in step S1205), theprocessing proceeds to step S1206. In step S1206, the system controlunit 209 determines the focus state as the in-focus state. Theprocessing then exits this flowchart. If the calculated defocus amountis larger than the in-focus management width (NO in step S1205), theprocessing proceeds to step S1207. In step S1207, the system controlunit 209 starts the flowchart of the saturated subject determination(step S1004).

In step S1208, if deemed Count is not zero, the system control unit 209checks the result of the saturated subject determination. If the stateof the saturated subject flag has been changed (YES in step S1208), theprocessing exits this flowchart. If deemed Count is zero, or if deemedCount is not zero and the state of the saturated subject flag remainsunchanged (NO in step S1208), the processing proceeds to step S1209.

In step S1209, the system control unit 209 determines whether deemedCount is equal to or larger than the first deemed CountTh. If deemedCount is equal to or larger than the first deemed CountTh (YES in stepS1209), the processing proceeds to step S1210. In step S1210, the systemcontrol unit 209 determines the focus state as the in-focus state. Theprocessing then exits this flowchart. If deemed Count is less than thefirst deemed CountTh (NO in step S1209), the processing proceeds to stepS1211. In step S1211, the system control unit 209 starts the flowchartof the focus detection processing (step S402). The processing thenreturns to step S1202. If the reliability decreases in step S1211, thesystem control unit 209 determines the focus state as the defocus state.The processing then exits this flowchart (not illustrated).

A method for preventing defocus by changing the deemed in-focus widthhas been described above. Another method for preventing defocus bychanging the number of deemed in-focus drives will be described belowwith reference to FIGS. 13 and 14. The operations in steps S1301 toS1307 illustrated in FIG. 13 are similar to those in steps S1001 toS1007 illustrated in FIG. 10, and redundant descriptions thereof will beomitted.

If the defocus amount is larger than the in-focus management width (NOin step S1306), the processing proceeds to step S1308. In step S1308,the system control unit 209 determines whether the defocus amount isequal to or less than the first deemed in-focus width. In step S1309,the system control unit 209 determines the ON/OFF state of the saturatedsubject flag determined in step S1304. If the saturated subject flag isOFF (NO in step S1309), the processing proceeds to step S1311 (stepS1011). In step S1311, the system control unit 209 starts the firstdeemed in-focus drive. The processing exits this flowchart. If thesaturated subject flag is ON (YES in step S1309), the processingproceeds to step S1310. In step S1310, the system control unit 209starts a second deemed in-focus drive illustrated in FIG. 14. Theprocessing then exits this flowchart.

The second deemed in-focus drive illustrated in FIG. 14 differs from thefirst deemed in-focus drive (step S1011) only in threshold value ofdeemed Count in step S1409, i.e., second deemed CountTh larger thanfirst deemed CountTh is set. More specifically, the number of deemedin-focus drives which is performed for a case where a saturated subjectis detected is larger than the number of deemed in-focus drives which isperformed for a case where no saturated subject is detected.

Thus, even in a case where lens drive is insufficient and cannot bedriven to achieve focus with the first deemed CountTh, lens drive can becontinued with second deemed CountTh, resulting in an improved focusingrate.

In this way, the focusing rate can be improved by increasing the numberof deemed in-focus drives and the time duration thereof in a case wherea saturated subject is detected. This effect can also be obtained byremoving (canceling) the limitations including the limited number ofdeemed in-focus drives and the limited time duration thereof.

To simplify the descriptions, a case where only one focus detectionregion (AF region) is set, has been described above with reference toFIG. 6. However, the effect of the present exemplary embodiment can alsobe obtained even in a case where the correlation calculation isperformed for a plurality of AF regions, and a region to be subjected toautomatic focusing is automatically selected based on the result of thecorrelation calculations.

As described above, the present exemplary embodiment makes it possibleto improve the focusing rate in an image including a high-luminancesubject, by detecting a misdetected saturated subject and then suitablychanging the determination criterion before terminating lens drive.

<Details of Lens Drive (Step S403) According to Second ExemplaryEmbodiment>

Lens drive (step S403) according to a second exemplary embodiment of thedisclosure will be described below with reference to FIG. 15. Forcomponents of an imaging apparatus 10 according to the second exemplaryembodiment equivalent to those of the imaging apparatus 10 (thelens-interchangeable camera system 10) according to the above-describedfirst exemplary embodiment, redundant descriptions will be omitted.

In step S1501, the system control unit 209 determines the ON/OFF stateof the saturated subject flag. If the saturated subject flag is OFF (NOin step S1501), the processing proceeds to step S1503. In step S1503,the system control unit 209 sets the defocus amount selected in stepS511 to the lens drive amount (drive amount). If the saturated subjectflag is ON (YES in step S1501), the processing proceeds to step S1502.In step S1502, the system control unit 209 multiplies the defocus amountselected in step S511 by m (>1) and sets the product to the lens driveamount (drive amount). In step S1504, the system control unit 209 drivesthe lens by the drive amount set in step S1001.

In this way, in a case where a saturated subject is detected, drivingthe lens by a defocus amount larger than the defocus amount calculatedthrough the correlation calculation enables a quick exit from thedefocus state with small (no) variation in the defocus amount, and thusquickly obtaining the in-focus state. Although, in the present exemplaryembodiment, the system control unit 209 sets the defocus amountmultiplied by m to the drive amount, the effect of the present exemplaryembodiment can be obtained by setting a predetermined value, forexample, 10 Fδ.

As described above, the present exemplary embodiment makes it possibleto improve the focusing rate in an image including a high-luminancesubject, by detecting a misdetected saturated subject and then suitablychanging the lens driving method.

<Details of Lens Drive (Step S403) According to Third ExemplaryEmbodiment>

Lens drive (step S403) according to a third exemplary embodiment of thedisclosure will be described below with reference to FIG. 16. Forcomponents of an imaging apparatus 10 according to the third exemplaryembodiment equivalent to those of the imaging apparatus 10 according tothe above-described first exemplary embodiment, redundant descriptionswill be omitted. Operations in steps S1601 to S1607 illustrated in FIG.16 are similar to those in steps S1001 to S1007 illustrated in FIG. 10,and redundant descriptions thereof will be omitted.

If the defocus amount is larger than the in-focus management width (NOin step S1606), the processing proceeds to step S1608. In step S1608,the system control unit 209 determines the ON/OFF state of the saturatedsubject flag. If the saturated subject flag is OFF (NO in step S1608),the processing proceeds to step S1610. In step S1610, the system controlunit 209 determines whether the defocus amount is equal to or less thanthe first deemed in-focus width. If the defocus amount is larger thanthe first deemed in-focus width (NO in step S1610), the processingreturns to step S1601. If the defocus amount is equal to or less thanthe first deemed in-focus width (YES in step S1610), the processingproceeds to step S1611. In step S1611, the system control unit 209starts the first deemed in-focus drive. The processing then exits thisflowchart. If the saturated subject flag is ON (YES in step S1608), theprocessing proceeds to step S1609. In step S1609, the system controlunit 209 determines the focus state as the defocus state. The processingthen exits this flowchart.

In a case where a saturated subject is detected in a state where thedefocus amount does not reach the in-focus management width (in thedefocus state), as described above, the system control unit 209determines the focus state as the defocus state. This enables avoidingan error that the focus state is determined as the focus state in thedefocus state.

In one embodiment, the imaging apparatus 10 includes a notification unitfor issuing a notification to the user when a saturated subject isdetected in a state where the defocus amount does not reach the in-focusmanagement width (in the defocus state). More specifically, in stepS405, the notification unit changes the color of a defocus frame,flashes the frame, or separately displays a saturated subject flag icon.The notification unit issues a notification that the defocus stateresults due to the saturated subject flag. More specifically, thenotification unit notifies the user that keeping pressing the switch SW1again enable the in-focus state to be obtained or that manually movingthe lens to an extent to obtain a state in which the focus state isclose to in-focus state and performing automatic focusing enable theuser to obtain the in-focus state.

The system control unit 209 may record a captured image in a recordingmedium in association with attribute information indicating a “saturatedsubject”. This enables an icon indicating a saturated subject to bedisplayed also in reproducing the captured image, allowing the user toeasily identify a captured image of the saturated subject.

As described above, the present exemplary embodiment makes it possibleto improve the focusing rate in an image including a high-luminancesubject, by detecting a misdetected saturated subject and then suitablychanging the determination criterion before terminating lens drive.

As described above, the present exemplary embodiments make it possibleto improve the focusing accuracy in an image including a high-luminancesubject, by detecting a misdetected saturated subject and then suitablychanging the determination criterion before terminating lens drive andthe lens driving method.

Accordingly, the focusing accuracy is prevented from degrading even inperforming a focusing operation on a saturated subject as a mainsubject.

OTHER EMBODIMENTS

Embodiment(s) of the disclosure can also be realized by a computer of asystem or apparatus that reads out and executes computer executableinstructions (e.g., one or more programs) recorded on a storage medium(which may also be referred to more fully as a ‘non-transitorycomputer-readable storage medium’) to perform the functions of one ormore of the above-described embodiment(s) and/or that includes one ormore circuits (e.g., application specific integrated circuit (ASIC)) forperforming the functions of one or more of the above-describedembodiment(s), and by a method performed by the computer of the systemor apparatus by, for example, reading out and executing the computerexecutable instructions from the storage medium to perform the functionsof one or more of the above-described embodiment(s) and/or controllingthe one or more circuits to perform the functions of one or more of theabove-described embodiment(s). The computer may comprise one or moreprocessors (e.g., central processing unit (CPU), micro processing unit(MPU)) and may include a network of separate computers or separateprocessors to read out and execute the computer executable instructions.The computer executable instructions may be provided to the computer,for example, from a network or the storage medium. The storage mediummay include, for example, one or more of a hard disk, a random-accessmemory (RAM), a read only memory (ROM), a storage of distributedcomputing systems, an optical disk (such as a compact disc (CD), digitalversatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, amemory card, and the like.

While the disclosure has been described with reference to exemplaryembodiments, it is to be understood that the disclosure is not limitedto the disclosed exemplary embodiments. The scope of the followingclaims is to be accorded the broadest interpretation so as to encompassall such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2019-086266, filed Apr. 26, 2019, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An apparatus comprising: an image sensorconfigured to output a signal for focus detection processing; one ormore processors; and memory storing instructions that, when executed bythe one or more processors, cause the apparatus to perform operationsincluding: detecting a defocus amount of an image of a target subject tobe subjected to the focus detection processing based on the signal forthe focus detection processing; controlling a focusing lens movementbased on the defocus amount; and determining whether the target subjectto be subjected to the focus detection processing is a saturatedsubject, wherein, in a case where a state where a variation in thedetected defocus amount or a variation in a moving amount of an imagingplane is smaller than a predetermined value continuously occurs apredetermined number of times or continues for a predetermined timeduration, the target subject to be subjected to the focus detectionprocessing is determined to be a saturated subject in the determination.2. The apparatus according to claim 1, wherein the operations furthercomprise detecting a pixel of which the signal for the focus detectionprocessing is saturated, and wherein, in a case where the state wherethe variation in the detected defocus amount of the image of the targetsubject to be subjected to the focus detection processing or thevariation in the moving amount of the imaging plane is smaller than thepredetermined value continuously occurs the predetermined number oftimes or continues for the predetermined time duration, and where apredetermined number of pixels of which the signal is saturated aredetected in the detection, the target subject is determined to be asaturated subject in the determination.
 3. The apparatus according toclaim 1, wherein, in a case where the detected defocus amount of theimage of the target subject to be subjected to the focus detectionprocessing is within a predetermined range, the target subject isdetermined to be a saturated subject in the determination.
 4. Theapparatus according to claim 1, wherein, in a case where the state wherethe variation in the detected defocus amount of the image of the targetsubject to be subjected to the focus detection processing or thevariation in the moving amount of the imaging plane is smaller than avariation in a defocus amount expected based on a moving amount of thefocusing lens moved in the control continuously occurs the predeterminednumber of times or continues for the predetermined time duration, thetarget subject is determined to be a saturated subject in thedetermination.
 5. A method comprising: detecting, as focus detection, adefocus amount based on a signal for focus detection processing;controlling a focusing lens movement based on the defocus amount; anddetermining, as saturation determination, whether a subject to besubjected to the focus detection processing is a saturated subject,wherein, in a case where a state where a variation in the detecteddefocus amount of an image of the subject to be subjected to the focusdetection processing or a variation in a moving amount of an imagingplane is smaller than a predetermined value continuously occurs apredetermined number of times or continues for a predetermined timeduration, the subject to be subjected to the focus detection processingis determined to be a saturated subject in the saturation determination.6. The method according to claim 5, further comprising: detecting apixel of which the signal for the focus detection processing issaturated, and wherein, in a case where the state where the variation inthe detected defocus amount of the image of the target subject to besubjected to the focus detection processing or the variation in themoving amount of the imaging plane is smaller than the predeterminedvalue continuously occurs the predetermined number of times or continuesfor the predetermined time duration, and where a predetermined number ofpixels of which the signal is saturated are detected in the detection,the target subject is determined to be a saturated subject in thedetermination.
 7. The method according to claim 5, wherein, in a casewhere the detected defocus amount of the image of the target subject tobe subjected to the focus detection processing is within a predeterminedrange, the target subject is determined to be a saturated subject in thedetermination.
 8. The method according to claim 5, wherein, in a casewhere the state where the variation in the detected defocus amount ofthe image of the target subject to be subjected to the focus detectionprocessing or the variation in the moving amount of the imaging plane issmaller than a variation in a defocus amount expected based on a movingamount of the focusing lens moved in the control continuously occurs thepredetermined number of times or continues for the predetermined timeduration, the target subject is determined to be a saturated subject inthe determination.
 9. A computer readable storage medium storing acomputer-executable program of instructions for causing a computer toperform a method, the method comprising: detecting, as focus detection,a defocus amount based on a signal for focus detection processing;controlling a focusing lens movement based on the defocus amount; anddetermining, as saturation determination, whether a subject to besubjected to the focus detection processing is a saturated subject,wherein, in a case where a state where a variation in the detecteddefocus amount of an image of the subject to be subjected to the focusdetection processing or a variation in a moving amount of an imagingplane is smaller than a predetermined value continuously occurs apredetermined number of times or continues for a predetermined timeduration, the subject to be subjected to the focus detection processingis determined to be a saturated subject in the saturation determination.10. The computer readable storage medium according to claim 9, furthercomprising: detecting a pixel of which the signal for the focusdetection processing is saturated, wherein, in a case where the statewhere the variation in the detected defocus amount of the image of thetarget subject to be subjected to the focus detection processing or thevariation in the moving amount of the imaging plane is smaller than thepredetermined value continuously occurs the predetermined number oftimes or continues for the predetermined time duration, and where apredetermined number of pixels of which the signal is saturated aredetected in the detection, the target subject is determined to be asaturated subject in the determination.
 11. The computer readablestorage medium according to claim 9, wherein, in a case where thedetected defocus amount of the image of the target subject to besubjected to the focus detection processing is within a predeterminedrange, the target subject is determined to be a saturated subject in thedetermination.
 12. The computer readable storage medium according toclaim 9, wherein, in a case where the state where the variation in thedetected defocus amount of the image of the target subject to besubjected to the focus detection processing or the variation in themoving amount of the imaging plane is smaller than a variation in adefocus amount expected based on a moving amount of the focusing lensmoved in the control continuously occurs the predetermined number oftimes or continues for the predetermined time duration, the targetsubject is determined to be a saturated subject in the determination.